How to set up aliases

What is an alias?

An alias is an additional email address you can create that will also deliver to your Inbox.

Aliases allow you to have different email addresses which all deliver to your one FastMail account, without needing to buy multiple accounts. This can help you to sort email. For example, you might have a sales@mydomain.com address for sales inquiries, and a press@mydomain.com address for news inquiries.

A distribution list is a type of alias, where the target is a group in your address book. Any message sent to the alias is forwarded on to all members of the group. This makes it easier to manage an address such as sales@example.com that needs to be distributed to a group of people. Distribution lists are intended to be for internal use only

Only administrators for an account can configure aliases.

Aliases cannot be used as your username when you log in; you must always use the full account username.

How to create an alias

You'll see a table with any current aliases you have. Use the "New Alias" button to add a new entry.

Aliases can be used to direct email to other users, even non-FastMail ones. See the Deliver to section below for a detailed description of how delivery works.

The Restrict senders option controls who can send mail to this alias. An alias can be limited to only allow FastMail users to access it (effective if you want to keep the alias available to members of your Family or Business account), or everyone, or nobody (disabled but the name is still reserved).

The SRS column should be left unchecked unless required. See the information on SRS rewriting.

Creating an alias also creates a matching account identity. This lets you send mail from your account using the email address matching that alias. You can customise other settings too, such as your signature.

If you're replying to mail that has been sent to an alias, FastMail automatically selects the correct alias to reply from! You won't be responding to a technical support enquiry from the sales email address.

How to disable an alias

You can disable an alias by selecting "Reject (bounce) all mail to this address" in the Restrict senders section of the alias, then clicking "Save". Any further email sent to that alias will now bounce (be returned to the sender as undeliverable).

How to remove an alias

To delete an alias, click the "Del" link in the far right of the row. This will cause any email sent to the alias to bounce, but will allow another user to create that alias in the future, unless you own the domain of the alias.

Alias delivery

Email sent to an alias will be forwarded on to the email address (or addresses) specified in the Deliver to section. By default, the target of all aliases is your user. You can, however, change the target of an alias to be any other user, including other FastMail users or a completely external email address.

You can target multiple users by adding multiple email addresses. If you do that, a copy of each email will be delivered to each target address. This can be a useful way to direct a copy of all email to a separate backup account at another provider. To do that, create a user and set up an alias that targets both your user and the external account you want backups to go to. Then, when you tell people about your email address, tell them your alias address, never your account's address.

You can target a contact group, so mail gets sent to every member within that group: useful for internal distribution lists.

You can also change targets to use plus addressing. Commonly, you might want email sent to a particular alias to go into a certain folder. The easiest way to do this is to use plus addressing. If you have a folder "aliasmessages", set the target to be youraddress+aliasmessages@fastmail.com and any email sent to the alias will automatically be put in the "aliasmessages" folder.

Note: alias targeting occurs before spam scanning or any rules are applied to a message.

Catchall/Wildcard Alias

External targets and SRS rewriting

On the aliases screen, there is an SRS checkbox for each alias. This can be useful if you have an external target (non-FastMail email address) for one of your aliases, and the target server you're forwarding to uses SPF to block emails.

SPF is a way for domain owners to authorise only particular servers to send email with a particular SMTP MAIL FROM envelope. The problem is that when email is forwarded by a service, the SMTP MAIL FROM envelope should be preserved. When that happens, it looks like the forwarding service is trying to send email with the same SMTP MAIL FROM envelope as the original service, which is blocked because the forwarding service hasn't been authorised. This is a bug with the design of SPF. There is a (fairly ugly) way to work around this though, and it's called SRS rewriting.

You can enable SRS rewriting for email sent to a particular alias just by enabling the SRS checkbox on that alias. We don't recommend enabling SRS unless you need to (i.e. emails aren't being forwarded correctly).

To get an idea of what SRS is, and what it does, here's an example. Say I have an alias abc@fastmail.com that targets xyz@gmail.com:

Someone sends an email from their Yahoo account def@yahoo.com to abc@fastmail.com. So the email has an SMTP MAIL FROM envelope of def@yahoo.com and an SMTP RCPT envelope of abc@fastmail.com.

We accept the email, and see it's an alias with target xyz@gmail.com. We forward the email with the SMTP RCPT TO envelope of xyz@gmail.com, and by default preserve the SMTP MAIL FROM envelope of def@yahoo.com.

However at this point, Gmail looks at the SMTP MAIL FROM envelope, sees @yahoo.com, does an SPF check and says "hold on, 66.111.4.25 (one of FastMail's outgoing IPs) hasn't been authorised by SPF to send email with an SMTP MAIL FROM envelope of @yahoo.com". It therefore rejects the message: SPF has broken forwarding.

When you activate SRS, we change the following.

We accept the email, and see it's an alias with target xyz@gmail.com. We forward the email with the SMTP RCPT TO envelope of xyz@gmail.com, and we alter the SMTP MAIL FROM envelope of def@yahoo.com to use SRS rewriting which creates something like SRS0+abcd=Cw=yahoo.com=def@srs.messagingengine.com. Since @srs.messagingengine.com is a domain we control, so there's no SPF issue.

If for some reason the email ends up bouncing, the NDN will be sent back to SRS0+abcd=Cw=yahoo.com=def@srs.messagingengine.com, which we'll get, then unwrap and send back to def@yahoo.com.